Sawshark rostral denticle (IMAGE) Penn State Caption A rostral denticle of Ischyrhiza mia, a species belonging to an extinct group of sawfishes that lived in North American waters during the late Cretaceous period, around 100 to 65 million years ago. The sample was recovered from a rock formation in New Jersey. Credit Todd Cook, Penn State (Courtesy: Wiley Publications) Usage Restrictions Educational use only License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.